1. Field of the Invention
The present invention relates to a locking device of a casing. More particularly, the present invention relates to a locking device of a casing applied to an information product such as a notebook, a PDA, a cell phone and the like.
2. Description of Related Art
Referring to FIG. 1, a first prior art-locking device includes buckling matching portions 20a protruding from edges on the same side of a cover 31a and a seat 32a of a casing, respectively, and two movable buckles 10a located relative to the buckling matching portions 20a for the closing and opening the casing.
The first prior art-locking device is operated by first moving the two movable buckles 10a, respectively, in opposite directions and then to lift vertically the cover 31a, such that the case is opened. The direction of the lifting of the cover 31a doesn't correspond to the motion of the movable buckles 10a, and is not ergonomically pleasing. Furthermore, the alignment between the movable buckle 10a and the buckling matching portion 20a often doesn't add to easy use of the prior art-locking device because of slides between the buckling matching portions 20a. 
As shown the FIG. 2 and FIG. 2A, a second prior art-locking device includes an upper buckling mechanism 20b disposed on a cover 31b of a casing and a lower buckling mechanism 10b disposed on a seat 32b of the casing and matching the upper buckling mechanism 20b for buckling and locking to each other.
The upper buckling mechanism 20b has an upper hook 21b, while the lower buckling mechanism 10b has a release button 11b and a slot 12b relative to the upper hook 21b. However, complex components and assembly steps are expensive to manufacture. Further, operation of the second prior art-locking device is ergonomically displeasing, involving first inwardly pushing the release button 11b and then vertically lifting the cover 31b to open the casing, such that the direction of the lifting of the cover 31b doesn't correspond to the motion of the release button 11b. 
Hence, the examples of prior art mentioned above obviously have disadvantages and an improved locking device is needed.